From the SouthPark episode TMI. According to Randy Marsh, you can calculate your Adjusted Penis Size (or TMI) with the following formula:
((L*D)+(W/G))/(A^2)
Length times Diameter plus Weight over Girth divided by Angle of the tip squared

Randy Marsh has a penis that is 4.4 inches in length. Its angle is 32 degrees. It's flaccid girth is 1 inch in diameter. His balls are 7 cm from the base. Randy notes that the drift of his penis is 4 cm to penis right and its dead weight is 4.5 Kg. Therefore, Randy's adjusted penis size is 6.3 inches.